The availability and accessibility of health care services to vulnerable populations is a matter of increasing importance to U.S. public policy makers. Using a descriptive-correlational design, this nursing study is intended to be a preliminary investigation to identify and describe factors that influence the use of formal cardiac rehabilitation programs by residents of sparsely populated rural states. Cardiac rehabilitation programs are a key component in the return to optimal physical and psychological health in patients with coronary disease. The specific aims are to examine the effects of (1) predisposing factors (demographic and social-structural characteristics, intent to use the service, health beliefs, and locus of control); (2) enabling factors (financial and environmental characteristics, perceived and actual service availability, and rurality); and (3) need factors (perceived health status and functional ability) on the use of rural cardiac rehabilitation programs. The combined effects of these factors on program use will also be examined. A random sample of 200 adult post-myocardial infarction, angioplasty, and coronary artery bypass surgery patients from 3 Montana hospitals will participate. The sample will be stratified by week of hospitalization. Data will be generated with paper and pencil questionnaires at 3 points in time: prior to hospital discharge, 2 weeks after discharge, and 1 week after completion of the rehabilitation program. The first questionnaire packet will be completed 1 to 2 days prior to discharge. Questionnaire packets 2 and 3 will be mailed to the participants. Follow-up phone calls will be made to increase the return rate. Data will be analyzed using multiple regression. Findings will be used to plan nursing intervention studies to promote use of cardiac rehabilitation services by rural residents.